As others have mentioned in passing, these old 1980's era ATB's weigh a ton. Manufacturers hadn't yet figured out that they didn't need to overbuild the frames so much. ATB's got significantly lighter into the 1990's.
I'm not convinced it's worthwhile to spend hundreds of dollars on buying and fixing up a 30+ lb tank, other than for nostalgia, especially when a brand new $99 Walmart ATB would completely blow the doors off of it on any kind of a ride. I myself don't see the advantage of owning something like that, but YMMV.